1. Field of the Invention
The present invention relates to a fluid ejection device, a fabrication method and an operating method thereof, adapted for an ink-jet printing head; and more particularly to a micro-electromechanical system (MEMS) fluid ejection device, a fabrication method and an operating method thereof.
2. Description of Related Art
To date, the ink-jet technology includes the bubble ink-jet technology and the piezoelectric ink-jet technology.
FIGS. 1A and 1B are schematic drawings showing an ink-jet head and an operation of the prior art bubble ink-jet technology. Referring to FIG. 1A, in the ink-jet head 100 adopted by the prior art bubble technology, the ink 104 is heated by a heater 102 for generating the bubble 106. Thereafter, the ink 104 is ejected from a nozzle 108 under the pressure of the bubble 106.
Referring to FIG. 1B, when the heater 102 stops heating, the bubble 106 in the ink 104 will not be inflated and remain flat as the result of cooling down. The surface tension of the ink 104 will create tensile force to pull back the ink 104. Accordingly, the operation of the thermal sensing ink-jet technology is performed. The printing speed of the bubble ink-jet technology is about micro-second level. The disadvantage is that the ink is easily ejected due to pressure and the ejection force of the ink cannot be controlled. The ink is adversely affected by law of inertia at the nozzle, resulting in non-uniformity or ink residuals. The other disadvantage is that, because the ink-jet head of the bubble ink-jet technology is usually under high temperature situation due to use of heater, and therefore the ink-jet head is easily damaged, especially in absence of ink therein.
FIGS. 2A-2C are schematic drawings showing an ink-jet head and an operation of the prior art piezoelectric ink-jet technology. Referring to FIG. 2A, the ink-jet head 200 of the prior art piezoelectric ink-jet technology uses a quartz crystal 202 to control the ejection of the ink 204. The ink-jet head 200 comprises a nozzle 208. When electricity is applied to the quartz crystal, the quartz crystal 202 generates a fixed oscillation frequency. When electricity applied to the quartz crystal is removed, the ink is pulled back.
Referring to FIG. 2B, when electricity is applied to the quartz crystal 202, the quartz crystal 202 expands and ejects the ink 204 from the nozzle 208. Because the piezoelectric ink-jet technology does not need thermal transformation, the damage the to ink-jet head due to thermal issue can be avoided.
Referring to FIG. 2C, when the supply of electricity to the quartz crystal is cut, the quartz crystal 202 shrinks to the original size for pulling the ink 204 back. The printing speed of the piezoelectric ink-jet technology is also about micro-second level. The problem is that it is not possible to further reduce the quantity of ejected ink.